South Korean President Lee Myung Bak will ask China's leaders this week to use their influence to lean on North Korea to show restraint amid a delicate transition to a new leadership.

Lee will hold a summit with China's president, Hu Jintao, in Beijing and will discuss ways to develop the strategic partnership between the two nations and cooperative measures for peace and stability on the Korean Peninsula, the South Korean president's office said in a statement.

Lee's three-day trip to China, his second in four years, begins Monday.

South Korea has said its primary foreign-policy goal this year is maintaining stability on the divided peninsula as its unpredictable neighbor embarks on a third generation of dynastic rule following Kim Jong Il's death last month.

Little is known about Kim's chosen successor, his son Kim Jong Un, who in his late 20s and who will be relying on a coterie of trusted members of the military and political elite to act as minders while he cements his grip on power.

Both South Korea and the United States have urged China, North Korea's main ally and benefactor, to help restrain the new leadership from staging any hostile acts.

Analysts say the young Kim may order a so-called provocation -- such as a small-scale military attack, a missile launch, or a nuclear test -- to burnish a hardline image with the country's powerful military.

Over the past week, North Korea, which has twice tested nuclear devices, has stepped up its use of hostile language against South Korea.

China voiced its support for North Korea's new leadership soon after Kim Jong Il's death was announced.

South Korea's ambassador to China, Lee Kyu Hyung, said last week that his country would continue to raise the issue of China's unwillingness to condemn North Korea when it provokes South Korea.

'Probematic'

In 2010, South Korea criticized China for refusing to censure North Korea for torpedoing a South Korean warship, killing 46 sailors. North Korea denied it sank the vessel.

It is problematic because China has appeared to take an attitude of protection and support for North Korea, while the North sometimes makes military provocations and implements some incorrect policies, Lee Kyu Hyung told South Korea's Yonhap news agency.

South Korea would continue to raise the issue and make efforts to persuade China to change that attitude, he said.

China backed North Korea during the 1950-53 Korean War, while the United States fought for South Korea. The United States still has about 28,000 troops in South Korea.

Lee and Hu are also expected to discuss how the two nations will push preliminary talks to launch formal negotiations for a free-trade agreement.

Since 2008, South Korea and China have held a series of joint feasibility studies on a possible free-trade deal and reached an agreement to exchange their views on sensitive issues.

The two leaders will also discuss the rising number of Chinese fishing boats caught illegally fishing off South Korea's west coast. Last December, a South Korean coastguard was killed while trying apprehend a Chinese vessel.

(Editing by Robert Birsel)